This invention pertains to a bidirectional current supply circuit, and more particularly, to such a circuit which includes adjusters which enable independent-level-control of current flowing in reverse directions through a load connected to the circuit. For the purpose of illustration herein, a preferred embodiment of the circuit is described in connection with transcutaneous nerve stimulation which is used for pain relief purposes.
A conventional bidirectional current supply circuit, similar to that disclosed in U.S. Pat. No. 4,102,347, entitled "Electronic Pain Control System", includes a single adjuster for controlling the level of current flowing through a load connnected to the circuit. Thus, the current flowing in reverse directions is always of the same level.
While there are applications for which this kind of an arrangement is entirely satisfactory, there are others where it is desirable to apply current in reverse directions of different levels. One of these applications concerns devices known as transcutaneous nerve stimulators which, essentially, are pulsed current supply circuits intended for connection through a pair of electrodes to a person's skin for the purpose of creating electrical current nerve stimulation. Such a device is used quite frequently for pain relief.
Nerves have a polarization characteristic such that negative-going pulses--that is, when the electrode over the pain site is a cathode--provide substantially more effective stimulation than positive--going pulses. If a person has a single pain site, the conventional common level-control current supply circuit provides the necessary pain relief. However, when a person has two areas of pain, the conventional circuit requires that two pairs of electrodes be used. This is necessary because different nerve sites require different levels of stimulation.
A general object of the present invention is to provide a bidirectional current supply circuit which includes independent-level-control of current flowing in reverse directions through a load connected to the circuit and a mode switch for optional operation with common-level-control.
More particularly, the present invention proposes a circuit wherein level control is provided by adjusters arranged substantially in parallel circuit with each other, and a switch, connected in series with the adjusters and the circuit, having a pair of switch conditions, one of which provides for common level-control of current flowing in reverse directions, similar to that provided in a conventional circuit, and the other of which provides for operation with independent current level-control.
With this kind of arrangement, a person, through the use of only two electrodes, can provide pain relief at either one site or concurrently at two sites. The relief of pain at two sites is thus provided, as far as the person operating the circuit is concerned, with only the addition of a mode switch and an additional adjuster.
These and other objects and advantages which are attained by the invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.